Background
Although urban malaria transmission is low and seasonal, it remains a major public health problem. This study aimed at demonstrating the presence of
Anopheles mosquitoes and their potential to transmit malaria in urban settings.
Methods
Two cross-sectional surveys were carried out in Blantyre District, Malawi, during the dry and wet seasons of 2008 and 2010, respectively. A map of
Blantyre was divided into a grid of 400 cells, of which 60 cells were randomly selected. Five households located within 100 m from the centre of each
selected cell were enrolled, a standard questionnaire was administered, and indoor resting mosquitoes were sampled.
Results
In 2008 and 2010, a total of 960 and 1045 mosquitoes were collected, respectively.
Anopheles funestus
comprised 9.9% (n = 95) and 10.3% (n = 108) during
the two surveys, respectively.
Anopheles gambiae sensu lato (s.l.) was rarely detected during the second survey (n = 6; 0.6%). Molecular identification was
performed on samples collected during the first survey, and
An. funestus sensu stricto (s.s.) was the only sibling species detected. All the
Anopheles mosquitoes
were collected from households located in rural areas of Blantyre and none from urban areas.
In univariate analysis, the presence of open eaves was associated with increased
Anopheles prevalence, both during the dry (incidence rate ratio, IRR =
4.3; 95% CI 2.4 – 7.6) and wet (IRR = 2.47; 95% CI 1.7 – 3.59) seasons. Chances of detecting
Anopheles spp. decreased with increasing altitude (IRR =
0.996; 95% CI 0.995 – 0.997) and during the dry season, but increased during the wet season (IRR = 1.0017; 95% CI 1.0012 – 1.0023). These factors
remained significant following a multiple Poisson regression analysis. No association was found between insecticide-treated bednet ownership and the
number of
Anopheles mosquitoes detected.
Conclusions
The presence of
An. funestus s.s and
An. gambiae s.l. in the periphery of Blantyre city was an indication that malaria transmission was potentially taking
place in these areas.
